This invention relates to laryngeal mask assemblies.
It is common practice to use airways known as laryngeal masks for the administration of anaesthetic and ventilation gases to a patient. These airways comprise a tube with an inflatable mask or cuff at one end, the tube being inserted in the patient's mouth so that one end is located in the hypopharynx and so that the mask forms a seal in this region with the surrounding tissue. Laryngeal masks are described in, for example, U.S. Pat. No. 5,355,879, U.S. Pat. No. 5,305,743, U.S. Pat. No. 5,297,547, U.S. Pat. No. 5,282,464, GB 2267034, U.S. Pat. No. 5,249,571, U.S. Pat. No. 5,241,956, U.S. Pat. No. 5,303,697, U.S. Pat. No. 5,477,851, GB 2249959, GB 2111394, EP 448878, U.S. Pat. No. 4,995,388, GB 2205499, GB 2128561, GB2294642 and GB 2298797.
Introducers have also been described, such as in GB 2259454, in which the introducer is placed in the patient's mouth and the laryngeal mask is slid along a channel in the introducer.
Laryngeal masks have several advantages over endotracheal tubes, which are longer and seal with the trachea below the vocal folds. Laryngeal masks do, however, have several problems. It is possible, for example, during insertion, for the epiglottis to enter and block the bore of tube. One solution to this is to place flexible cross bars at the patient end of the tube, in the manner described in GB 2205499. This, however, involves an obstruction at the patient end of the tube, which may be undesirable.
Another problem arises from the fact that the tube must be sufficiently soft and flexible, in order to conform to the anatomy and be atraumatic, yet a certain amount of force is needed to introduce the mask assembly to the correct position. One method of insertion of the mask is to slide its tip against the soft palate as it is introduced, in order to stimulate a swallowing action while preventing a retching reflex. In order to do this, the clinician has to hold the tip of the mask against the soft palate with his finger, pushing his finger into the patient's mouth to its full extent, as the mask is inserted. Clinicians with smaller hands can have difficulties with this procedure. Another problem arises from the soft nature of the tube, in that it is prone to bend and twist during insertion, making it difficult to position correctly.